Plate heat exchange unit



' Aug. 18, 1959 Filed March 28, 1958 o. s, McGUFFEY 2,900,175

PLATE HEA'lf EXCHANGE UNIT 5 Sheets- Sheet 1 7 INVENTOR. ORTGN $.McGUFFEY ATTQ RN EYS Aug. 18, 1959 o. s. McGUFFEY 5 PLATE HEAT EXCHANGE UNIT Filed March 2a, 1958 s Sheets-Sheet 2 FIG- 4- INVEN TOR.

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PLATE HEAT EXCHANGE UNIT Filed March 28, 1958 5 Sheets-Sheet 3 INVENTOR. ORTON S. MGUF'FEY ATTORN YS Aug. 18, 1959 o, s. MCGUFFEY 2,900,175

' PLATE HEAT EXCHANGE UNIT Filed March 28I 1958 5 Sheets-Sheet 4 FIG- 9- INVEN TOR. oRToN 3. MGUFFEY ATTORNEYS Aug. 18, 1959 o. s. MCGUFFEY PLATE HEAT EXCHANGE UNIT 5 Sheets-Sheet 5 Filed March. 28, 1958 F Cl [2.

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INVENTOR. ORiyN S MGLJFF' Y BY 5% ATTORNEYS United States Patent PLATE HEAT EXCHANGE UNIT Orton S. McGulfey, Lansing, Mich., assignor to Tranter Manufacturing, Inc., Lansing, Mich., a corporation of Michigan Application March 28, 1958, SerialNo. 724,749

Claims. (Cl. 257-256) The present invention relates to an improved plate-type heat exchange unit having a built-in circulatory coil. Units of this type are commonly and widely employed as immersion heaters for liquid tanks or like vessels in which a variety of processing operations are performed. The present application is a continuation-in-part of my copending application, Serial No. 534,925, filed September 19, 1955, now abandoned.

Internal coil type plate heat exchange units as heretofore fabricated commonly have transverse header and longitudinal distributory ducts or passages separated from one another along weld zones at which the plates of the unit are secured in facing relation, the transverse header ducts communicating'with and being of greater width than the longitudinally extending circulatory passages for greater flow handling capacity. It follows that the welded plate connections on either side of the headers are necessarily loaded considerably more heavily by the pressure of the heat transfer fluid than other welds, as those spanned by the plates at the longitudinal passages. In consequence, it is a common occurrence for welded zones on one or the other side of the header, or between the header and the ends of the longitudinal welds, to tear free under beam loading stress and destroy. the unit locally, rendering it useless.

There is also another operational drawback in plate units of this type, in that the distribution and flow of the heat transfer medium (and its condensate in the case of a heater) from header to circulating or distributor passages, and vice versa, has usually not been uniform and smooth. The pressure fluid may be unduly directed into one set of passages, resulting in bypassing of others and non-uniform thermal transfer across the surface of the unit.

A uniformly distributed, non-turbulent and smooth flow of a heating medium through a heat transfer unit is, of course, to be desired, but equally desirable is a flow of its condensate through and out of the unit in the easiest and most expeditious manner. Upon entering any given duct or passage of the unit the heating medium, for example, steam, condenses as it traverses the passage and forms as a film on the inner surface of the latter; and the principle underlying the present invention is that this condensate film, if it builds up to an excessive degree, detracts from the efliciency of heat transfer through the wall of the passage to as great or greater extent as external fouling of the unit. This principle is given effect, in the unit, according to the several embodiments of the invention by devising internal weld formations, at which the constituent plates of the unit are secured to one another, of such shape and disposition as to subdivide the interior of the unit into two or more independent sets of passages, each independently receiving a metered proportion of the heating medium at the units intake, and each conveyingthe medium in independent fashion, and: without interference, along parallel paths to a discharge portion of the plate unit.

Reaction of the condensate film to heat transfer is "Ice greatly dissipated, since it is pushed along the paths of the respective sets in a much easier and more rapid way.

It is therefore one of the general objects of the present invention to provide an internal coil-type plate heat exchange unit adapted to internally circulate a fluid heat exchange medium under relatively high pressure and with optimum thermal efliciency; and to these ends the unit has improved provisions to increase its pressure containing ability by diminishing the distance of area bridging Welds, thus reducing internal beam loading stressunder pressure.

Coupled with this is the further general object of improving the distribution and flow of the pressure fluid and condensate through the unit, thereby to improve efliciency in a marked degree. This is accomplished by improved provisions both to insure a uniform distribution of the heat exchange medium, upon initial entry, into several distinct sectors of the unit, and to insure the flow of the medium and its condensate through these sectors in independent, preferably parallel paths, without any possibility of interference or starving any one heat transfer area of the unit as compared with another, and thereby retarding the transfer actionof the unit as a whole. Condensate film at the internal transfer surfaces is thus dissipated with ease and rapidity; and the result is an average improvement in efficiency of from 22%27% as compared with prior plate type coil units of corresponding capacity.

In general, the plate unit of the invention is constructedof embossed plates welded together to provide the necessary transverse header and longitudinal circulatory or distributor passages on ducts, in which an improved scheme of welding the plates makes possible the better pressure containment and fluid distribution mentioned above.

In accordance with the invention, the transverse header and longitudinal circulatory or distributor formations, as embossed in the individual component plates ofthe heat exchange unit, are separated by internal weld zones, including zones of generally Z-shaped outline, whereby no internal circulatory passage in the unit is unsupported across a materially greater width than any other passage or duct portion. This signifies that, under a given high internal pressure, no duct' formation, in particular in the header duct portions of the unit, is loaded, in the manner of an end supported beam, under a total fluid pressure force materially in excess of that acting on any other duct formation.

At the same time the generally Z-shaped weld zone or zones which in part function to afford the desired divided header feature are so devised .as to define independent sets of distributor passages producing the desired improved uniformity of the heat distribution by better dissipating the action of condensate film in resisting heat transfer atthe internal surfaces of the plate. More specifically, it is an object of the invention to provide a plate-type heat exchange unit of the above character, in which longitudinally extending circulatory or distributor passages are separated by longitudinally extending weld zones at which the constituent shaped plates are secured to one another; and in which certain of these weld zones have extensions in the form of transversely extending, preferably right angled weld zones at the opposite ends thereof which lie in and subdivide intake or discharge header ducts or passages.

This arrangement not only has the advantage of produring the improved pressure containment and distribution of fluid flow mentioned above, but also improves the heat transfer unit structurally, particularly as regards its manufacture in an overall arcuate or circular outline for certain special installations. The subdividing of the intake and discharge headers makes it possible to keep the unit flat'at its intake and discharge areas, i.e., with the outer plate surfaces no farther apart in these zones than their outer surfaces at which the embossments forming the circulatory passages are formed. Thus, the split header affords adequate and uniform fluid handling capacity and pressure containment comparable to those of a non-split header design, and it can be roll formed to arcuate outline, whereas this is impractical in a unit in which headers of adequate capacity necessarily flare outwardly substantially beyond the remainder of their embossed surfaces.

The foregoing as well as other objects will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Fig. 1 is a top plan view of a plate-type heat exchange unit in accordance with one embodiment of the invention;

Fig. 2 is a fragmentary view in somewhat enlarged scale, partially in end elevation and partially broken away and in section, as along line 22 of Fig. 1;

Fig. 3 is a fragmentary, somewhat enlarged, view in transverse vertical section along the line 33 of Fig. 1;

Fig. 4 is a plan view of a unit in accordance with a modification of the principle of the invention as applied to a plate of a given capacity;

Fig. 5 is a plan view of another modification for a plate unit of a smaller size;

Fig. 6 is a broken plan view of an alternative form in a larger size;

Figs. 7 and 8 are fragmentary sectional views on lines 77 and 88, respectively, of Fig. 6, showing typical details of plate sectioning of a sort different from that of Fig. 3;

Figs. 9, 10, 11 and 12 are broken and partial views of still further modified embodiments of the invention in plate units of different sizes and fluid capacities;

Fig. 13 is a fragmentary plan view showing a plate unit in accordance with a further modification, in which a header opens transversely of the unit, rather than through an edge margin thereof; and

Fig. 14 is a fragmentary section on line 1414 of Fig. 13.

The improved built-in coil, plate-type heating unit in accordance with one embodiment of the invention shown in Figs. 1, 2 and 3 is generally designated by the numeral 10. It is fabricated in its entirety of a pair of like sheet-metal plates 11, 12 of a suitable rigid material resistant to erosion, or chemical attack by the liquid which it is intended to heat or cool, as an immersion type unit, as well as by the fluid which is internally circulated in unit as a heating or cooling agent.

In accordance with the invention as shown in Figs. 13, the plates 11 and 12 are embossed to provide vertical or transverse intake and discharge header formations, generally designated 13, 14 in Fig. 1 and connecting horizontal or longitudinal circulatory and distributor duct or passage formations 15 which open at their opposite ends to the respective duct formations 13, 14.

The plates 11, 12, in which these formations are incorporated by an embossing operation, are identical, the functions of the header duct formations 13, 14 being interchangeable. Thus, as illustrated, there are three horizontally or longitudinally extending weld zones 16 adjacent the top and bottom of each plate, as viewed in Fig. 1, which parallel one another in equally spaced relation to partially define four horizontally or longitudinally extending distributor passage formations 15. As will be understood, these weld zones lie coplanar with one another and with a flat marginal flange 17 which extends around the sides and ends of each of the plates 11, 12. The longitudinal, coplanar weld zones or formations terminate in a predeterminedly spaced relationship, approximately equal to the spacing of the Zones 16 from one another, to the flange 17 at one end of the plate.

In accordance with the invention, a pair of special, angularly shaped weld zones or formations of approximately Z-shaped outline-are provided on each of the plates 11, 12, inwardly of the series of three parallel formations 16 described above, these special formations being designated 18 and having the function of subdividing the respective vertical or transverse header formations 13, 14 to improve pressure containment and circulatory efiiciency in the manner contemplated by the invention, as generally described above.

Each of the special formations 18, which are exactly similar to one another, includes a horizontally or longitudinally extending weld zone length 19 arranged parallel to the weld formations 16 and of somewhat greater length than the latter; a first and longer, vertically or transversely extending header subdividing formation 21) integral with and at a right angle to the longitudinal portion 19; and a second and shorter, vertical or transverse formation 21 in a similar right angle, integral relation to the formation 19.

As illustrated in Fig. 1, the special Z-shaped weld formations 18 are in a nested relationship to one another, spaced by an intermediate set of intervening parallel straight weld zones 21' similar to the sets of zones 16 on either outer side of the formations 18, but offset slightly in the longitudinal direction relative to the latter. Thus, the transverse portion 21 of each special intermediate formation 18 lies" inwardly of, and in spaced parallel relation to the longer transverse portion 20 of the other special formation 18. The weld portions 20 are spaced inwardly of the respective marginal flanges 17 of the plate 11 or 12, a distance approximately equal to the spacing of the ends of the respective straight weld zone formations 16 from the margins 17; and the shorter transverse portions 21 are similarly spaced inwardly from the longer transverse portions 20.

It will also be noted that the ends of the respective weld zones 16 and 21 of the respective sets are longitudinally oifset or stepped slightly relative to one another, in a manner and for a purpose to be described.

The effect of all of this is to subdivide the width of the respective intake and discharge header formations 13 and 14, constituting in either of those formations three split header passage formations, 22, 23, 24, which are defined between adjacent ends of each set of straight longitudinal weld formations 16, a shorter transverse weld extension 21 of the special weld formation 18, a longer transverse extension 23 of a formation 18, and a coplanar end margin 17.

In completing the improved plate 10, the two plate components 11, 12 are placed in vertically registering relationship of their various respective weld formations 16, 18 and 21, which subdivide the center set of longitudinal passages and the sets on opposite sides thereof, and are then welded into a rigid internal coil assembly. An enlarged intake opening 25 of circular shape and substantial size is formed which opens through one side margin of the unit 10, and a similar discharge opening 26 is formed to extend through the opposite side margin and adjacent the opposite corner of the unit 10, in opposed relation to the opening 25. However, such an angled relationship of the passages 23, 24, featuring a Z-shaped intermediate weld or welds, is not essential in accordance with the invention, as the other illustrated embodiments make clear. The intake and discharge provisions may be arranged at a common side of the unit, 10 or otherwise, in accordance with the requirements of the installation.

In the joining of the plates 11, the margins 17. are preferably seam welded throughout their L-shaped lengths; whereas spot-welds are preferably employed in securing the internal. Zones 16, 18, 19, 20, 21 and 21' of the two plates to one another, as indicated by the reference numeral 27 in Fig.3.

Such spot-welds will be formed at the extreme ends of each of thestraight. longitudinal weld zone formations 16 and 21, at spaced points along the length thereof, as well as at spaced points along the length of the special angled formations 18, particularly along. the respective shorter and longer transverse extensions 21, 20, respectively, of the latter.

It is seen that a maximum width of any given transverse header passage subdivision 22, 23 or 24, is no greater than the width of any longitudinal distributor passage defined by the trough-like longitudinal formations- 15 of the coacting plates 11, 12. The longitudinal spacing of welds 27 along the weld zones may be of the order of i in a unit wherein the transverse passage spacings are up to 1".

An integral built-in coil heat transfer unit, fabricated as described, at least cuts in half the bridge distance or spacing between spot-Welds at critical points in its construction, hence, at least halves the total force acting on the metal between those welds to tear the same free. In this connection, it is desirable that the respective passage defining formations 15 of the plates 11, 12, as well as the sectional outline of the passage subdivisions 22, 23, 24 of transverse headers 13, 14, be of a curved circular section, so as to minimize possible whip action exerting increased stress on the critical weld points when the internal duct work of the unit is pressurized. I have found that by following the principles set forth above it is possible to produce a heat transfer unit which will successfully withstand a fluid pressure of 1000 pounds per square inch, enabling the manufacturer to supply a unit of 200 pounds per square inch rating, with a 5 to 1 safety factor.

In addition to greatly improved pressure containment, the plate unit 10 secures a better and more even distribution of the fluid heating or cooling medium in circulating therethrough, hence better thermal efiicienoy at all pressures. The Z-shaped weld formations 18 properly apportion the. pressure fluid entering the respective subdivided intake duct portions 22, 23, 24, and distribute it properly for divided and entirely independent flow of it and its condensate through the several sets of longitudinal distributor passages defined by the intermediate weld zones 21' and weld zones 16 on either outer side thereof.

This type of independent, parallel-path flow is of the greatest importance in that it facilitates and expedites the removal of condensate film forming within the passages. A heat medium, as steam, enters the divided or split header, is distributed as between the several sets of independent longitudinal passages, performs its function and condenses on the inner surfaces of the unit in the form of a film. However, the opposition of such film to rapid and efficient heat transfer is at a minimum, since there is a minimum opposition to its being pushed along the passages to the discharge header.

Further, in respect to the action at longitudinal circulatory passages 15, it is to be noted, referring to Fig. 1, that the ends of the respective longitudinal weld zones 16 and21' of each set of welds are arranged, subject to limitations imposed at the corners of the plate unit, in a slightly offset or progressively stepped relation to one another in the longitudinal sense. This stepping is designated S in all embodiments. Thus, with the unit 10 disposed vertically as in Fig. 1, or in a 180 inverted vertical position (inasmuch as it is interchangeable as regards its intake and discharge), the stepped relationship of the weld zones 16, 21 at their ends further improves the distribution into and through the respective longitudinal passages of the three sets, by giving enlarged access to the inner passages. In short, throughout the entire area of the plate unit 10 there is no likelihood of local excess surface heating or cooling, due either to improper bypassing of an undue proportion of the incoming fluidor trapping a portion, or both.

Moreover, at the opposite, discharge ends of the respective passages 15 (left hand end as viewed in Fig. 1) the longitudinally olfset or stepped relations at S also exist, but in the reverse sense (i.e., with the ends of weld zones 16 or 21 offset slightly outwardly beyond the ends of zones therebeneath). By this feature the advantage is had that any condensate from an upper passage 15 will not drop into a passage therebeneath, or onto the weld zones 16 or 21 of the latter passage. Erosion of the metal over a period of time by such drippage on a local zone is thus prevented. The overlap or stepping S is slight, in any of the embodiments shown, i.e., of the order of one sixteenth inch in a typical plate unit, and is shown exaggerated in the drawings for the purpose of clarity.

Fig. 2 of the drawings shows the enlarged header 25 of the embodiment under consideration. An advantage of subdividing the intake and discharge headers by the weld formations 18 is that not only does this permit adequate header capacity and pressure containment for a given size installation, it also enables the plates of the unit 10 to be kept flat atthe intake and discharge areas, i.e., with their outer surfaces no farther apart than the outer surfaces of the various embossments forming the longitudinal passages 15. To this end, the enlargement 25, as well as that at 26, may be formed by swedging the assembled plates to the desired size of intake or discharge mouth. It follows that the plate unit 10, and other embodiments to be described, may be roll formed after assembly to one another in a desired arcuate outline of any desired radius, with the header openings being swedged after the roll-forming operation. This is a decided advantage over previous plate-type heat transfer units of non-split header construction. and of corresponding header capacity and pressure containment. Theoutwardly flared header zones necessarily incorporated in such units make it impossible, as. a practical matter, to roll form the latter for special tank. installations.

Fig. 4 of the drawings shows an alternative embodiment of the principles of the invention, in that among other features the intake and discharge. openings of the plate unit, which is generally designated 30, are arranged to open through the same margin of the unit, in this case a longitudinal or horizontal margin, and, moreover, adjacent a corner end thereof. The unit 3% is fabricated of embossed sections secured to one another preferably by marginal seam welding and spot welding at the internal weld zones, as inFigs. 1, 2 and.3. Hence further illustration in respect of sectional details of this modification is not necessary. Sectional contours may be as shown in Fig. 3, or in the alternative as in Fig. 7, to be described.

The unit 30 of Fig. 4 may be typically produced in a rectangular outline of, say, 21 inches on its vertical or transverse dimension, and of any desired length in the longitudinal or horizontal direction. Thus, as apractical feature and in the interest of die standardization, it is practical in accordance with the invention to form the plates of .the unit 30 by assembling die parts which will properly emboss the two opposite longitudinal ends of the plate in a desired outline of weld zones at either end of a central die portion, as in the area between the vertical dot-dash theoretical lines A and B of Fig. 4, and such central die portion may be furnished in any desired length to afford longitudinal weld formations determined by the size of the installation in question.

In a similar way, multiple die parts may be employed to form subordinate component parts of the two end portions on either outer side of the. lines A and B. Such die parts may be, as determined by the weld contours at either plate end, of outlines such as are indicated between the horizontal dot-dash theoretical lines C, D and/or E, F.

It is seen that the principles of the invention aiford great flexibility and versatility as to the operations of manufacturing plate units in any of the various designs and sizes represented in the embodiments of Figs. 1, 4, 5, 6, 9, 10 and 11.

In the form shown in Fig. 4 there are two of the Z-shaped internal weld zones 31, 32, arranged in a nested relationship to one another similar to that of Fig. 1. An intake opening 33 and a discharge opening 34 of somewhat smaller size are shown, opening through the same upper corner margin of the plate unit 30. Intake 33 is in communication with an intake header or duct, generally designated 35, and the discharge opening 34 is in communication with a discharge header, generally designated 36; and in this case the discharge header 36 is subdivided for improved pressure containment, as well as improved distribution of outgoing fluid and/or condensate flow, by a weld zone 37 of laterally inverted L-shaped outline. This zone defines the parallel discharge header passages 38, 39 of reduced width.

A further weld zone 40 of similar inverted L-shaped outline separates the discharge header 36 from the intake header 35, terminating at an upper flared weld area 41 between the intake and discharge openings 33, 34. Divider weld zone 40 parallels the zone 37.

In respect to the remainder of the modified plate 36, the arrangement of the Z-shaped welds 31, 32 is generally similarto what is shown in Fig. 1. This is subject to the exception that, of the two left hand downturned outer and inner legs or ends 43, 44, respectively, of the Z-shaped formations, the former is brought farther down than the latter. Thus leg 43 controls the distribution of fluid or condensate into the bottommost of two discharge passages 45, 46 separated by the L- shaped divider 37, while the other leg 44 acts similarly in respect to the uppermost passage 46 of the two.

As for the opposite upstanding, outer and inner legs 48, 49, respectively, of the Z-welds 32, 31, they 'terminate coextensively in the vertical sense, and substantially as shown in Fig. 1.

As indicated specially by dotted line in Fig. 4, the offsetting S of the ends of the longitudinal weld zones of the several sets, i.e., the zones 50 between the horizontal reaches of Z-formations 31, 32, and the sets of longitudinal weld zones 51, 52 on either side of the latter, has the effect of better distributing the entry of pressure fluid from the subdivided passages 53 of intake header 35 to the respective sets. The offset or stepped relation S also better controls the flow at discharge, i.e., into the passages 45, 46 from the area G of generally rectangular outline shown in dotted line in Fig. 4.

It also prevents destructive erosion by dripping of condensate as mentioned above. The end extensions protrude beyond the vertical leg of the Z-section which separates one set of passages from the next one, thereby providing thorough access for all condensate intothe entrance of the discharge outlet passages 45, 46.

The unit 30 of Fig. 4 is one of good pressure-containing character and thermal efiiciency, both factors governed in a large measure by the provision of the Z- shaped internal welds and the relationship of the longitudinal welds to them and to one another. Distances or area bridging successive weld points or zones are substantially uniform through the structure, with the result that beam loading action under high internal pressure is locally equal throughout. As regards thermal efficiency, the unit 30 is improved in this respect due to better condensate dissipation and control, having this advantage in common with all of the other illustrated embodiments.

Fig 5 of the drawings depicts a heat transfer plate unit, generally designated 54, of lesser dimension in the vertical or transverse sense than that of Figs. 1 and 4, but incorporating the basic structure of Fig. 4, and its operational advantages. Here, in view of the diminished size, a single Z-shaped central divider weld 55 is employed. It has a horizontal portion or length 56 separating a set of intake passages 57, 58, 59 thereabove defined by a set of longitudinal weld zones 60 from a further set of intake passages 61, 62 therebelow separated by the longitudinal weld zone 63 on the opposite side of Z-weld 55.

A weld zone 64 of laterally inverted L-shaped outline, terminating in a flared marginal weld area between corner inlet and discharge openings 65, -66, separates a condensate outlet passage 67 from the passages 57, 58, 59, 61, 62. Weld oflsets or steps S are present; and the operation of this modification is essentially the same, with corresponding advantages in point of pressure containment and thermal efiiciency, as the two embodiments previously described.

The further modified embodiment shown in Fig. 6, is generally designated 68 and, as indicated by the dotdash theoretical lines AF, is capable of standardized production using the optional special dies for the several areas of the respective constituent plates of the unit, as governed by desired size and weld outline.

Since it is believed that. the principles of the invention are now clearly understood from what has been described in connection with Figs. 1 through 5, the various relationships characterizing the plate unit 68 will be only generally referred to and identified by reference numeral.

Thus, two nested internal, Z-shaped weld zones are generally designated 69, 70, with two horizontal or longitudinal weld zones 72 therebetween defining intermediate longitudinal fluid passages 73 in conjunction with the horizontal portions of the Z-welds 69, 70. Sets of further longitudinal weld formations 74 and passages 75 are disposed on opposite sides of the latter.

As in Fig. 5, there is a single laterally inverted L- shaped discharge header or passage 76 separated from the divided header intake passage 77 by a weld zone 78 of inverted L-shape. It will be noted that the downturned ends or legs 79, 80 of the Z-welds 69, 70 terminate coextensively at the horizontal entrance of the discharge passage 76-, substantially in the horizontal line of the L-shaped weld zone 78. Here again, the passage ends of the respective longitudinal weld zones 74 are oflset, stepped or staggered at S for the advantageous effects of distribution and erosion prevention.

An optional sectional formation of two component plates til, 82 of the unit 68 (or indeed any of the units shown), as an alternative to the section appearing in Fig. 3, is illustrated in Fig. 7. Duct or passage formations 33 are embossed Which are of obtusely angled cross section, with the apices thereof mildly rounded at 84, and the plates 81, 82 are secured together by the respective marginal seam and internal spot Welds 85 and 8 respectively. The result is a plate construction in which adequate flow capacity is had, while minimizing whip action likely to impose sudden and undue stress on the welds under heavy pressure.

Fig. 8 of the drawings shows an appropriate intake fitting 88, in dotted line, as applied to the marginal intake opening of the plate unit 68 of Fig. 6, this opening being designated 89, while the marginal discharge opening is designated 9% (Fig. 6). Openings 89 and 9% are prefably swedged to the desired size following the welding of the unit 68.

Figs. 9, l0 and ll of the drawings show three different contemplate embodiments of the invention in which the intake and discharge openings, in all three forms designated 92 and 93, respectively, open through a common side margin of the plate structure. Thus, in the modification of Fig. 9 these openings are in substantially spaced vertical or transverse relation to one another adjacent the respective ends of a transverse margin of the plate unit, which is in this instance generally designated 94. In the embodiment of Fig. 10, the openings are, as in 9 Figs. 4, and 6, at a common longitudinal or horizontal margin of theplate unit, generally designated- 96', while in Fig. 11 the plate unit 98- has anintake opening 92' and discharge opening 93 substantially spaced transversely from one another along one transverse margin.

In these three formations the principles of the invention are carried into effect by'weld formations, headers, ducts and passages similar to those employed in the preceding forms. Thus, in order-to avoid needless repetition, corresponding parts and relationships are in each form designated by corresponding referencev numerals. These provisions include the Z-shaped weld formations 3'90, the longitudinal weld. formations 193i and. passages 102 defined thereby, the intake and discharge headers or ducts 193, 104, respectively, and the laterally inverted L-shaped weld formations 105, 1%, one or both of the headers being equipped therewith, reducing the weld bridging distance. All three embodiments possess advantagesin regard to pressure containment and improved efficiency by reason of improved: uniformity of distribution of flow, as described in relation to the preceding modifications.

Fig. 12 illustrates a further modification in the form of a plate unit 108 of smaller size and simpler design than the embodiment of Figs. 1-3, but having in common with it the fact that the intake and discharge. ports or openings m9, Hti, respectively, are through, diagonally opposed corner edge zones, in this case on the vertical or transverse edges. Like the form of Fig. 1 these openings may be interchangeably used. The intermediate Z-shaped weld formation 111: has a leg 112' subdividing the header to which port 109 opens into passages 113, 114; and its opposite leg 115 similarly subdivides the otherheader'into passages 116, 117.. Two independent sets of passages, on either side of Z-weld 111, are sepmated by the respective longitudinal welds 118, 119.

The. improvements of the inventionv are not limited to plate structures in which the intake and discharge are through edge openings of the plate unit. Thus Figs. 13 and 14 show a typical installation in which a plate unit 120 has plates 121, 122 welded along marginal. and interior lines 123, 124, and embossments 125 providing passages'126 of the sort shown in Fig. 7. One of these has a terminal portion at whichthe embossment 125 is apertured at 127 at 90 tothe plane of the assembled plate unit 120; A tubular fitting 128 is appropriately shaped at its inner end to fit the embossment, and is welded or otherwise secured in pressure tight relation to the plate 121 about the aperture 127.

This type of plate unit is suitable for special installations in which a marginalheader opening is not practical or desirable; and the plate unit 1201 of Figs. 13 and 14 may be considered to incorporate all of. the other structural features described and shown in the other figures.

What I claim as my invention is:

l. A built-in coil type heat transfer unit for immersion heating and related heat transfer. operations involving the circulation through the unit of aheat transfer fluid under substantial pressure, said unit; comprising a pair of sheet metal plates assembled in: face-to-face relation and marginally sealed fluid tight to one another, at least one of said plates being: formed to'provide between the plates tubular, transversely extending intake and discharge headers and tubular, longitudinal distributor passages located between said headers, said. headers respectively communicating with intake and discharge openings through the sealed pla-te margin, said longitudinal distributor passages being separated from one another and intosets, including a center set and sets on opposite sides thereof, by zones of'substantially Z=shaped outline along which-said plates are secured to one another, which zones terminate substantially short of the respective opposite ends of the-plates between which said sets are disposed, there being a pair of such secured zones located between said intermediate set of longitudinal passages and the respective sets of passages on opposite sides thereof, which pair of secured zones are provided with transverse extensions at their opposite ends located in said respective headers, said extensions subdividing said headers into header passagesof lesser Width atv the ends of said longitudinal passages and said plates being secured together along said transverse extensions to reduce the fluid pressure beam loading of the plates in the zones of said headers.

2. A built-in coil type heat transfer unit for immersion heating and related heat transfer operations involving. the circulation through the unit of a heat transfer fluid under substantial pressure, said unit comprising a pair of sheet metal plates assembled in face-to-face relation and marginally sealed fluid tight to one another, at least one of said plates being formed to provide between the plates tubular, transversely extending intake and discharge headers and tubular, longitudinal distributor passages located between said headers, said headers respectively communicating with in take and discharge openings through the sealed plate margin, said longitudinal distributor passages being separated from one another and into sets, including a center set and sets onopposite sides thereof, by zones of substantially Z-shaped outline along which said plates are secured to one another, which zones terminate substantially short of the respective opposite ends of the plates between which said sets are disposed, there being a pair of such secured zones located between said intermediate set of longitudinal passages and the respective sets of passages on opposite sides thereof, which pair of secured zones are provided with transverse extensions at their opposite ends located in said respective headers and running toward the respective marginal openings of the latter, said extensions subdividing said headers into header passages of lesser width at the ends of said longitudinal passages and said plates being secured together along said transverse extensions to reduce the fluid pressure beam loading of the plates in the zones of said headers.

3. A built-in coil type heat transfer unit for immersion heating and related heat transfer operations involving the circulation through the unit of a heat transfer fluid under substantial pressure, said unit comprising a pair of sheet metal plates assembled in face-to-face relation and marginally sealed fluid tight to. one another, at least one of said .plates being formed to provide between the plates tubular, transversely extending intake and discharge headers adjacent and within respective opposite transverse ends thereof and tubular, longitudinal distributor passages extending between said headers, said headers opening through the sealed plate. margin, said longitudinal distributor passages being separated from one another by parallel longitudinal zones along which said plates are secured to one another, which zones terminate substantially short of said respective opposite plate ends, there being transverse end extensions of at least one of said longitudinal secured zones which are located in said respective headers and run toward the respective marginal openings of the latter, said extensions subdividing said headers into header passages of lesser width at the ends of said longitudinal passages and said plates being secured together along said transverse extensions to reduce the fluid pressure beam loading of the plates in the zones of said headers.

4. A built-in. coil type heat transfer unit for immersion heating and related'heattransfer operations involving the. circulation through the unit of a heat transfer fluid under substantial" pressure, said unit comprising a pair of sheet metal plates assembled in face-to-face relation and marginally sealed fluid tight to one another, at least one of said plates being formed to provide between the plates tubular, transversely extending intake and discharge headers adjacent and within respective opposite transverse ends thereof. and tubular, longitudinal distributor passages extending between said headers, said headers 11 opening through the sealed plate margin at diagonally opposed zones of said unit, said longitudinal distributor passages being separated from one another by parallel longitudinal zoes along which said plates are secured to one another, which zones terminate substantially short of said respective opposite plate ends, there being transverse end extensions of a pair of said longitudinal secured zones which are located in said respective headers and run toward the respective marginal openings of the latter, said extensions subdividing said headers into header passages of lesser width at the ends of said longitudinal passages and said plates being secured together along said transverse etxensions to reduce the fluid pressure beam loading of the plates in the zones of said headers.

5. A built-in coil type heat transfer unit for immersion heating and related heat transfer operations involving the circulation through the unit of a heat transfer fluid under substantial pressure, said unit comprising a pair of sheet metal plates assembled in face-to-face relation and marginally sealed fluid tight to one another, at least one of said plates being formed to provide between the plates tubular, transversely extending intake and discharge headers adjacent and within respective opposite transverse ends thereof and tubular, longitudinal distributor passages extending between said headers, said headers opening through the sealed plate margin at diagonally opposed zones of said unit, said longitudinal distributor passages being separated from one another and into sets, including an intermediate set and sets on opposite sides thereof, by parallel longitudinal zones along which said plates are secured to one another, which zones terminate substantially short of said respective opposite plate ends, there being a-, pair of such secured zones located between said intermediate set of longitudinal passages and the respective sets of passages on opposite sides thereof, which pair of secured zones are provided with transverse extensions at their opposite ends located in said respective headers and running toward the respective marginal openings of the latter, said extensions subdividing said headers into header passages of lesser width at the ends of said longitudinal passages and said plates being secured together along said transverse extensions to reduce the fluid pressure beam loading of the plates in the zones of said headers.

6. A built-in coil type heat transfer unit for immersion heating and related heat transfer operations involving the circulation through the unit of a heat transfer fluid under substantial pressure, said unit comprising a pair of sheet metal plates assembled in face-to-face relation and marginally sealed fluid tight to one another, at least one of said plates being formed to provide between the plates tubular, transversely extending intake and discharge headers adjacent and within respective opposite transverse ends thereof and tubular, longitudinal distributor passages extending between said headers, said headers opening through the sealed plate margin in substantially longitudinally spaced relation to one another, said longitudinal distributor passages being separated from one another by parallel longitudinal zones along which said plates are secured to one another, which zones terminate substantially short of said respective opposite plate ends, there being transverse end extensions of at least one of said longitudinal secured zones which are located in said respective headers and run toward the respective marginal openings of the latter, said extensions subdividing said headers into header passages of lesser width at the ends of said longitudinal passages and said plates being secured together along said transverse extensions to reduce the fluid pressure beam loading of the plates in the zones of said headers.

7. A heat transfer unit adapted to internally circulate a fluid heat transfer medium under substantial pressure, comprising a pair of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to afford fluid intake and discharge headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers communicating with the exterior of said unit and said plates being in contacting relation to one another in longitudinally extending secured zones separating said longitudinal passages and ending in adjacent spaced relation to at least one of said headers, said zones including at least one secured zone of substantially Z-shaped outline having a longitudinal portion separating passagm on opposite sides thereof and transverse portions each spaced inwardly of a secured margin of the plates and outwardly of one of the ends of a longitudinally extending secured zone, thereby to reduce the bridging distance and resultant beam loading of said plates between said last named margin and zone end when said plates are under internal pressure.

8. A heat transfer unit adapted to internally circulate a fluid heat transfer medium under substantial pressure, comprising a pair of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to afford fluid intake and discharge headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers opening marginally through said plates and said plates being in contacting relation to one another in longitudinally extending secured zones separating said longitudinal passages and ending in adjacent spaced relation to at least one of said headers, said zones including at least one secured zone of substantially Z-shaped outline having a longitudinal portion separating passages on opposite sides thereof and transverse portions each spaced inwardly of a secured margin of the plates and outwardly of one of the ends of a longitudinally extending secured zone, thereby to reduce the bridging distance and resultant beam loading of said plates between said last named margin and zone end when said plates are under internal pressure.

9. A heat transfer unit adapted to internally circulate a fluid heat transfer medium under substantial pressure, comprising a pair of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to afford fluid intake and discharge headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers communicating with the exterior of said unit and said plates being in contacting relation to one another in longitudinally extending secured zones separating said longitudinal passages and ending in adjacent spaced relation to at least one of said headers, as well as in transversely extending secured zones at least one of which is located in a header and subdivides the width of the latter, said zones including at least one secured zone of substantially Z-shaped outline having a longitudinal portion separating passages on opposite sides thereof and transverse portions each spaced inwardly of a secured margin of the plates and outwardly of one of the ends of a longitudinally extending secured zone, therebyto reduce the bridging distance and resultant beam loading of said plates between said last named margin and zone end when said plates are under internal pressure.

10. A heat transfer unit adapted to internally circulate a fluid heat transfer medium, comprising a pair of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to afford fluid intake and discharge headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers communicating with the exterior of said unit and said plates being in contacting relation to one another in longitudinally extending secured Zones separating said longitudinal passages and ending in adjacent spaced relation to at least one of said headers, said zones ,including at least one secured zone having a longitudinal portion separating passages on opposite sides thereof, there being a set of at least two longitudinal zones on one side of said longitudinal portion, the zones of which set have corresponding ends thereof arranged in longitudinally stepped relation to one another.

11. A heat transfer unit adapted to internally circulate a fluid heat transfer medium, comprising a pair of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to afford fluid intake and discharge headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers communicating with the exterior of said unit and said plates being in contacting relation to one another in longitudinally extending secured zones separating said longitudinal passages and ending in adjacent spaced relation to at least one of said headers, said zones including at least one secured zone having a longitudinal portion separating passages on opposite sides thereof, there being a set of at least two longitudinal zones on one side of said longitudinal portion, the zones of which set have corresport-ding opposite ends thereof arranged in longitudinally stepped relation to one another, with the transversely outermost thereof over-extending the inner at one end and being over-extended by the inner at the opposite end.

12. A heat transfer unit adapted to internally circulate a fluid heat transfer medium under substantial pressure, comprising a pair of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to afford fluid intake and discharge headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers opening marginally through said plates and said plates being in contacting relation to one another in longitudinally extending secured zones separating said longitudinal passages and ending in adjacent spaced relation to at least one of said headers, as well as in transversely extending secured zones at least one of which is located in a headerandsubdivides the width of the latter, said zones including at least one secured zone of substantially Z-shaped outline having a longitudinal portion separating passages on opposite sides thereof and transverse portions each spaced inwardly of a secured margin of the plates and outwardly of one of the ends of a longitudinally extending secured zone, thereby to reduce the bridging distance and resultant beam loading of said plates between said last named margin and zone end when said plates are under internal pressure, there being a set of at least two longitudinal zones on one side of said longitudinal portion of said Z-shaped zone, the zones of which set have corresponding opposite ends thereof arranged in longitudinally stepped relation to one another, with the transversely outermost thereof overextending the inner at one end and being over-extended by the inner at the opposite end.

13. A heat transfer unit adapted to internally circulate a fluid heat transfer medium, comprising a pair of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to afford a transverse header between the secured plates and longitudinal circulatory passages communicating therewith, said header communicating with the exterior of said unit and said plates being in contacting relation to one another in longitudinally extending secured zones separating said longitudinal passages and ending in adjacent relation to said header, certain of said secured zones including a transverse portion subdividing said header into independent and separated header passages and a longitudinal portion separating certain of said longitudinal passages on its opposite sides into independent sets of at least one passage each, which sets of separated longitudinal passages communicate respectively with said separated passages of said header whereby to provide for independent parallel flow of fluid through said respective header passages and said sets.

14. ,A heat transfer unit adapted to internally circulate a fluid heat transfer medium, comprising a pair'of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to aflord transverse headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers communicating with the exterior of'said unit and said plates being in contacting reltaion to one another in longitudinally extending secured zones separating said longitudinal passages and ending in adjacent reltaion'to saidrheaders, said secured zones including transverse portions subdividing each of said headers into independent and separated header passages and a longitudinal portion separating certain of said longitudinal passages on its opposite sides into independent sets of at least one passage each, which sets of separated longitudinal passages communicate respectively with said separated passages of said headers whereby to provide for independent parallel flow of fluid through respective ones of said header passages and said'sets.

15. A heat transfer unit adapted to internally circulate a fluid heat transfer medium, comprising a pair of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to afford transverse headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers communicating with the exterior of said unit and said plates being in contacting relation to one another in longitudinally extending secured zones separating said longitudinal passages and ending in adjacent relation to said headers, said secured zones including a generally Z-shaped zone having transverse portions subdividing said respective headers into independent and separated header passages and a longitudinal portion connecting 'said transverse portions and separating certain of said longitudinal passages on its opposite sides into independent sets of at least one passage each, which sets of separated longitudinal passages communicate respectively with said separated passages of the respective headers, whereby to provide for independent parallel flow of fluid through said respective header passages and said sets.

16. A heat transfer unit adapted to internally circulate a fluid heat transfer medium, comprising a pair of plates marginally secured together in face to face relation, at least one of which is provided with concave formations facing the other to afford transverse headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers communicating with the exterior of said unit and said plates being in contacting relation to one another in longitudinally extending secured zones separating said longitudinal passages and ending in adjacent relation to said headers, said secured zones including a generally Z-shaped zone having transverse portions subdividing said respective headers into independent and separated header passages and a longitudinal portion connecting said transverse portions and separating certain of said longitudinal passages on its opposite sides into independent sets of at least one passage each, which sets of separated longitudinal passages communicate respectively with said separated passages of the respective headers, whereby to provide for independent parallel flow of fluid through said respective header passages and said sets, the plates of said transfer unit having their outer side surface extremities in parallel planes throughout practically the entire side area of the unit.

17. A heat transfer unit adapted to internallycirculate a fluid heat transfer medium under substantial pressure, comprising a pair of plates seam welded marginally together in face to face relation and provided with outwardly embossed, concave formations to afford fluid intake and discharge headers between the secured plates and longitudinal circulatory passages communicating therewith, said headers communicating with the exterior of said unit through the margin of said plates and said plates being spot Welded to one another in longitudinally extending zones separating said longitudinal passages and ending in adjacent spaced relation to at least one of said headers, as well as in transversely extending secured zones at least one of which is located in a header and subdivides the width of the latter, said zones including at least one zone of substantially Z-shaped outline having a longitudinal portion separating passages on opposite sides thereof and oppositely extending transverse portions each spaced inwardly of a welded margin of the plates and outwardly of an adjacent end of a longitudinal Welded zone, thereby to reduce the bridging distance and resultant beam loading of the welds of said plates between said last named margin and zone end when said plates are under internal pressure, there being a set of at least two longitudinal welded zones on one side of said longitudinal portion of said Z-shaped zone, the zones of which set have corresponding opposite ends thereof arranged in longitudinally stepped relation to one another, with the transversely outermost thereof over-extending the inner at one end and being over-extended by the inner at the opposite end.

18. A heat transfer unit in accordance with claim 17, in which said unit is generally rectangular and said headers open through opposed marginal edges of said unit.

19. A heat transfer unit in accordance with claim 17, in which said unit is generally rectangular and said headers open through opposed marginal edges of said unit and adjacent diagonally opposed corners of the latter.

20. A heat transfer unit in accordance with claim 17, in which said unit is generally rectangular and said headers open through a single marginal edge of said unit.

21. A heat transfer unit in accordance with claim 17, in which said unit is generally rectangular and said headers open through a single marginal edge of said unit and adjacent one end of said edge.

22. A heat transfer unit in accordance with claim 17, in which said unit is generally rectangular and said headers open through a single marginal edge of said unit and in substantially spaced relation adjacent the respective ends of said edge.

23. A heat transfer unit in accordance with claim 17, in which said unit is generally rectangular and said headers open through a single longitudinal marginal edge of said unit.

24. A heat transfer unit in accordance with claim 17, in which said unit is generally rectangular and said headers open through a single longitudinal marginal edge of said unit and adjacent one end of said edge.

25. A heat transfer unit in accordance with claim 17, in which said unit is generally rectangular and said headers open through a single transverse marginal edge of said unit. V v

26. A heat transfer unit in accordance with claim 17, inwhich said unit is generally rectangular and said headers open through a single transverse marginal edge of said unit and in substantially spaced relation adjacent the respective ends of said edge.

27. A heat transfer unit in accordance with claim 17, in which. said unit is generally rectangular and in which said headers open through opposed longitudinal marginal edges of the unit and adjacent diagonally opposed corners of the latter.

28. A heat transfer unit in accordance with claim 17, in which said unit is generally rectangular and in which said headers open through opposed transverse marginal edges of the unit and adjacent diagonally opposed corners of the latter.

29. A heat transfer unit in accordance with claim 17, in which at least one of said headers opens through a side surface of one of said plates.

30. A heat transfer unit adapted to internally circulate a fluid heat transfer medium, comprising a pair of plates marginally secured together in face to face relation and having means of generally Z-shaped outline therebetween affording a pair of spaced transverse headers between the secured plates and independent and parallel longitudinal circulatory passages independently communicating with said headers, said headers communicating with the exterior of said units, said Z-shaped means including transverse portions subdividing said respective headers into independent and separated header passages and a longitudinal portion between said transverse portions separating certain of said longitudinal passages on its opposite sides into independent sets of at least one passage each, which sets of separated longitudinal passages communicate respectively with said separated header passages, whereby to provide for independent parallel flow of fluid through said respective header passages and said sets.

References Cited in the file of this patent UNITED STATES PATENTS 1,823,788 Dewoitine Sept. 15, 1931 2,156,544 Raskin May 2, 1939 2,200,426 Lehman May 14, 1940 2,496,558 Philipp Feb. 7, 1950 2,626,130 Raskin Jan. 20, 1953 2,699,325 Hedin Jan. 11, 1955 2,848,200 Jacobs Aug. 19, 1958 FOREIGN PATENTS 674,264 France Oct. 21, 1929 

